Yellow Dog is a disturbing book, but its opening pages create a mood of excited reassurance: Martin Amis at his best, in all his shifting registers, his drolleries and ferocities, his unsparing comic drive, his aesthetic dawdlings and beguilements, his wry, confident relish of his own astonishing effects. The pace is smartish, and there are three strands of narrative, each with its particular social register and verbal colour, distinct as the worlds within a Dickens novel, and with a comparable sense of latent connectedness.

There is Xan Meo, the actor who has also written a book of short stories, and is married to a beautiful American academic; Xan is coshed over the head outside a Camden bar in the first chapter, and the resultant changes to his personality, the newly assertive id, the reawoken violence of his gangland origins, are the painful, the deliberately not-quite-funny heart of the novel. Xan is someone who has settled down, who has made himself good and sober and loyal, and the regression, the "de-enlightenment", caused by the head injury has a nightmarish compulsion to it. Amis is wonderful on "the violence hormones still squirreling around in him: voluptuous killers of pain and reality". Social disruption, people saying and doing quite the wrong things at the wrong time, is the mainstay of an unsentimental kind of comedy; but Amis makes more painful use of it here, since it is the sentimental life that is brutalised by it, in the violent demands Xan makes on his wife and the creeping and horrified sexual interest he feels for his four-year-old daughter Billie. This is, even so, a tricky matter to situate in a novel of comic hyperbole, but Amis can do it; indeed the amnesiac rereading of the normal world harks back more than 20 years, to the case of Mary Lamb in Other People .

Above and below Xan's story run two extravagantly funny satires, on the royal family and the yellow press, which is just getting its hands on a royal item of unprecedented invasiveness - a film of the teenaged Princess Victoria in the bath. No year is given, but as often in Amis, the satirical exaggeration of today's concerns seems to carry us into an even more deplorable near-future. We are given an alternative royal line, springing from the real one at some unspecified past date, and replacing it in an otherwise unaltered history. Thus the present king Henry IX's grandfather was John II, and his father, Richard IV, was blown up by the bomb that killed the real Mountbatten. Certain details are borrowed from the actual royal family (Henry shares the late Princess Margaret's fondness for singing "My Old Man's a Dustman" round the piano), but Amis avoids direct satire of so pummelled a subject for a more forgiving vein of sublime silliness. King Henry, dull and shy, "senescent with ennui", but decently perplexed by the "dreadful world we're living in", suggests a memory of the bemused monarch in Ronald Firbank's The Flower Beneath the Foot, and there are several moments when Amis's oblique narration and dotty fantasy are surprisingly akin to Firbank's; while the depiction of Henry's household seems also to draw on Waugh and Wodehouse. The king, indeed, might be a dim but distinguished member of the Drones Club, taking months to get through dog-eared books of puzzles, and coming unstuck on "these bally cryptics". The description of him playing patience and solitaire in a child like pretence of having limitless time before an unwelcome engagement is so silly and so acute as to bring a tear to the eye.

Meanwhile, at the Morning Lark, the journalist Clint Smoker, a classic Amis mixture of failure, aggression and completely hopeless longing, is busy writing pun-crippled celebrity gossip. The Lark is a kind of down-market version of the Daily Sport, its readers known professionally as "wankers", its pages impermeable to all news but capable of the occasional intervention in current affairs ("You're forgetting the enormous groundswell of wanker response to our Nuke the Nonces campaign"). Clint is a setter-up of stories, a broker in unreality, but also, as an inhabitant of Amis's bad-sex/no-sex world, a needy believer in such unrealities. Throughout the novel he pursues an email courtship with a woman called k8, whose emails go to all lengths to incorporate abbreviations: "i've got a new str@agem: not washing. let's c how long he can st& the s10ch!" or "r u o fait with the poetry of Ezra £?" This is really the language of texting, and it is indeed a textual joke, ruefully admitted by Amis, who gives us a further list of such things that he hasn't quite bothered to put into an e-mail ("i must -", "a 2nd 9-hour operation on his :"). It comes as no surprise that k8, when Clint finally meets her ("How's your father, love?" "decim8ed"), is herself a kind of textual joke.

It doesn't, I hope, give too much away to say that the tiny hinge of the action is the title story in Xan's collection Lucozade; Amis buffs will recognise that this story, in which Xan has ill-advisedly mentioned someone working in Las Vegas for Joseph Andrews, is closely akin to Amis's own story "State of England", collected in Heavy Water (1998), and containing, by a further intertextual twist, a good deal of background on Mal, the very person with whom in the novel Xan has a conversation about "naming" Joseph Andrews. It's not quite clear what we're to make of this. A further strand, concerning an approaching comet and an aircraft destroyed in flight by a coffin that breaks loose in the hold, sounds that apocalyptic note recurrent in Amis's comedies, but does not feel essential to this one.

Everything Amis writes is highly structured, but Yellow Dog gives signs of quite bristling organisation, in its three parts and its subdivided and subheaded chapters. They create a vague sense of anxious coercion, of asserted significance, of the author insisting on his terms and inventions. Few writers are more tirelessly in charge than Amis, and the tirelessness, in the bigger books like London Fields and The Information , seemed at times to upbraid the feebler stamina of the reader. Yellow Dog is a shorter-breathed book altogether, and there is perhaps a sense, in its second half, of the insistent management being a distraction from the thinness of the content. No harm at all in changing the tempo and playing with the reader's expectations, but after the confident agility of the first half the second half falls back on oddly bald chunks of back-story, presented through the talk and the dictated memoirs of Joseph Andrews himself, the exiled Mr Big. Amis has always been interested in really bad men, and can't help but be funny about violently bad behaviour: "In the old days," recalls Andrews of a criminal partner, "he'd have himself committing crimes even in his alibis . He'd go: 'I was never in on the Brink-Mats lark. I was busy flogging this condemned Argie beef.' Or: 'How could I have been in on the Waterloo jewellers? I was up West, demanding with menaces.' A very dishonest man, Tony Eist." Amis acknowledges the memoirs of "Mad" Frankie Fraser, and one feels he could spool out this kind of heightened pastiche for ever. When the action moves to Lovetown, or "Fucktown", the southern California city devoted entirely to the making of porn, there are still some good walk-ons, such as the indignantly under-valued porn-actor Sir Dork Bogarde, but the protracted explications of porno lore read like a slightly too earnest magazine article, and the novel's energy runs into the sand; for once Amis doesn't take us with him.

Several details of this novel that most linger in the mind are to do with the children: four-year-old Billie's levitating walk of inquisitive anxiety when she visits her father in hospital; her "unreadable contentment" in finding that he has changed; the episode when the two of them see a fox on the roof of the garden shed, the animal's "entreating frown with its depths of anxiety". They are moments of magical vigilance and great emotional delicacy, intimations of a quite different kind of writer that Amis could be, or would be, perhaps, were it not for the demands of his devastating comic gift.

Alan Hollinghurst's new novel, The Line of Beauty, is published next year.